In the field of graphic arts, an image-forming system providing super high contrast (in particular, 10 or more in gamma) is required for improving the reproduction of continuous tone images by dot images or the reproduction of line images.
For obtaining high contrast photographic characteristics using a stable developer, there are known methods using hydrazine derivatives as described in U.S. Pat. Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606, 4,221,857, 4,269,929, 4,650,746, 4,243,739, and 4,618,574, JP-A-No. 62-150343 and JP-A-No. 62-90646, and Japanese Patent Application No. 62-43704. (The term "JP-A" as used herein means an "unexamined published Japanese patent application".)
According to these methods, photographic characteristics of super high contrast and high speed are obtained and further it is possible to add a sulfite at a high concentration to a developer, whereby the stability of the developer to air oxidation is greatly improved as compared to a lith developer.
However, although this imaging system is suitable for a high contrast system of very high speed, the system is unsuitable for daylight type low-speed photographic light-sensitive materials, which are widely used for contact work in printing plate making steps.
Methods of obtaining daylight type low-speed photographic light-sensitive materials containing hydrazines are described in JP-A-No. 60-14038, JP-A-No. 60-162246, and JP-A-No. 61-238049 and Japanese Patent Application No. 62-65116.
Silver halide photographic materials generally incorporate a light absorptive compound in silver halide emulsion layer(s) or other hydrophilic colloid layer(s) for absorbing light of specific wavelengths, for the purposes of controlling the speed of the photographic light-sensitive materials, improving the safelight safety, controlling the color temperature of light, and preventing the occurrence of halation and, in particular, for the purpose of controlling the balance of sensitivities in multilayer color photographic materials.
In particular, a silver halide photographic material which is used for a photographic printing plate making process or more specifically a daylight type photographic light-sensitive material contains a dye absorbing ultraviolet light or visible light in the light-sensitive emulsion layer or a layer disposed between a light source and a light-sensitive emulsion layer thereof.
Also, this dye is incorporated in a hydrophilic colloid layer disposed between a light-sensitive silver halide emulsion layer and the support of a photographic light-sensitive material for preventing the occurrence of halation.
The dyes which are used for these purposes must satisfy various factors: the dyes must be easily dissolved out from the bleached silver halide photographic materials during photographic processing to prevent the occurrence of substantial color stain; the dyes must not adversely affect silver halide photographic emulsions (by fogging or desensitization); the dyes must not diffuse into other layers from the layer colored by the dyes; the dyes must have good spectral absorption characteristics according to purpose; and further the dyes must be excellent in stability with the passage of time and must not change their properties in solutions or silver halide photographic materials.
Various efforts have been made to find dyes capable of meeting these factors. For example, there are proposed pyrazolone oxonol dyes described in British Patent No. 506,385; barbituric acid oxonol dyes described in U.S. Pat. No. 3,247,127; azo dyes described in U.S. Pat. No. 2,390,707; styryl dyes described in U.S. Pat. No. 2,255,077; hemioxanol dyes described in British Patent No. 584,609; merocyanine dyes described in U.S. Pat. No. 2,493,747; cyanine dyes described in U.S. Pat. No. 2,843,486; and methylene type benzilidene dyes described in U.S. Pat. No. 4,420,555. Also, Japanese Patent Application No. 61-249871 discloses a daylight type silver halide photographic material containing a dye having .lambda..sub.max shorter than 390 nm.
When the layer containing this dye functions as a filter layer or an antihalation layer, it is necessary that it only is selectively colored by the dye, and that other layers are not substantially colored by the dye.
However, there is a problem that even when the dye is incorporated in a layer other than the silver halide emulsion layer(s), the dye diffuses into the emulsion layer(s) to prevent the irradiation by exposure light of the emulsion layer(s), whereby the line width control of characters in contact work and the tone control of dot images is lost, i.e., practically, the capability of broadening the width of the character line of the original to some extent or broadening the dot area of the original to some extent. In contact work in a printing plate making process, the capability of correcting the images is required for adding an artistic expression to the images formed, in addition to the capability of reproducing the same line width or dot area as that of original.
For solving this problem, it is known to localize an acid dye having a sulfo group or a carboxyl group in a specific layer of a silver halide photographic material using a mordant.
As such a mordant, there are known ethylenically unsaturated polymers having a dialkylaminoalkyl ester residue described in British Patent No. 685,475; reaction products of a polyvinyl alkyl ketone and aminoguanidine described in British Patent No. 850,281; and vinylpyridine polymers and vinylpyridinium cation polymers described in U.S. Pat. Nos. 2,548,564, 2,484,430, 3,148,061 and 3,756,814. When cationic mordants having in the polymer a secondary amino group, a tertiary amino group, a nitrogen-containing heterocyclic group or a quaternary cation group are used, the acid dyes can be effectively mordanted.
However, these cationic mordants sometimes cause an electrostatic interaction with gelatin which is ordinarily used as a hydrophilic colloid for photographic light-sensitive materials and surface active agent having an alcoholate group, a carboxylate group, a sulfonate group or a sulfate group, which is usually used as a coating aid in the case of producing photographic light-sensitive materials, whereby the coating properties of photographic coating compositions are reduced.
Also, in the case of using such a mordant, it frequently occurs that the acid dye described above diffuses into other photographic layers and hence it is necessary to use a large amount of the mordant to prevent the diffusion of the acid dye. However, in such a case it is difficult to completely prevent the diffusion of the acid dye, and the thickness of the layer containing a large amount of the mordant is increased, to cause the problem that the dye remains in the photographic light-sensitive materials after processing.
Furthermore, for processing a light-sensitive material for making a printing plate, processing called "reduction" using a reducer is typically performed for controlling density and gradation, and the reducer contains a water-soluble iron complex as a reducing agent. However, if a cationic mordant is used in the photographic light-sensitive materials being processed by such a reducer, the mordant undergoes electrostatic bonding with the iron complex to form yellow stains by the iron complex.
For solving such a problem, dyes the diffusion of which into other layers is restrained and which are decolored during processing to give reduced color stain are disclosed in Japanese Patent Application No. 62-43704. However, although the dyes show excellent diffusion resistance and decoloring properties, it has been found that the use of the dyes reduces gamma and also reduces the quality of white lettering on solid background.
It is also common to increase the surface roughness of a silver halide photographic material by incorporating a matting agent in the protective layer of the photographic light-sensitive material for reducing its adhesive properties upon contact of the light-sensitive materials or contact of the light-sensitive material and the apparatus for processing it; for improving static prevention; and also close-contact with a vacuum on contact exposure. Spherical matting agents are generally used for improving the transparency of the photographic material after processing and efficiently increasing the surface roughness. However, it has been found that when such spherical matting agents are incorporated in a protective layer together with the non-diffusible dye, relatively small "black pepper" spots form in the edge portions of dot images or line images and in fine white lines having a line width of less than about 40 .mu.m. This small "black pepper" phenomenon different from ordinary relatively large black pepper caused by infectious development in the unexposed portions of a high speed high contrast light-sensitive material. The existence of the relatively small black pepper in the edge portions and white lines results in reducing the smoothness of edges (hereinafter, referred to as "edge smoothness") in dot images or line images. Also, the small black pepper in fine white lines of characters causes fogging of the characters, which reduces the image quality.
As a method of preventing the formation of the relatively large black pepper occurring in unexposed portions, there are known a method of preparing a silver halide in the presence of an iridium salt and increasing the silver iodide content at the surfaces of the silver halide grains as described in JP-A-No. 61-29837; a method of adding a mercapto compound having a water solubilizing group as described in JP-A-No. 61-52640; and a method of adding an acid material to reduce the pH of the surface of the layer below 5.8.
These methods are effective for the prevention of the relatively large black pepper formed in unexposed portions, but do not prevent the relatively small black pepper formed in edge portions of dot images or line images or the fine white lines of characters. A method for preventing the occurrence of such small black pepper has been keenly desired.